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First, apropo nothing whatsoever (except that I happened upon it in a search for [ chia ] here in the forums), I hope everyone has read MIchael's Nutrition and Supplementation for Veg(etari)ans.
Now, my question: I hear and read much about people getting their omega-3 needs met by flax seeds or flax seed oil, or, for some of us, fish, others, supplements, but I don't hear much about chia seeds. Is there some problem with them I haven't seen?
I created an Excel spreadsheet with 250 calorie amounts of nuts, a few seeds, and a few other fatty items in order to help guide my fatty food choice, and was amazed at how nutritious chia seeds are!
They're bland-tasting, to be sure -- is that why people don't get excited about them? Otherwise, lots of minerals, but no scary amounts of Cu or Mn (though not really low Mn), far more vitamins than most nuts or seeds, even a lot of carotenoids. Fairly low SFA, to boot. And then all that ALA.
Is there some hidden danger?
Zeta

All,
Like we've seen for cardiovascular disease, eating fish can be a mixed blessing. The omega-3 fatty acids (DHA/EPA) are thought to be beneficial, particularly for brain function. But the mercury, PCBs and other contaminants that bioaccumulate in the fat of fish may also have harmful effects. This new study[1] (thanks to Al Pater!) looks at the association between consumption of fish, plant omega-3s, brain mercury levels and Alzheimer's disease and brain mini-strokes.
What they found is a bit nuanced, but worth thinking about.
They gave 550 quite elderly but initially dementia-free people in several US nursing homes a yearly dietary questionnaire to measure their weekly intake of fish, DHA/EPA and the plant-derived omega-3 Alpha Linolenic Acid (ALA) until they died. Over an average follow-up of 4.5 years, 286 of the participates died (average age 89!). These folks' brains were autopsied to measure mercury levels and to look for physical signs of Alzheimer's disease (plaques and tangles) as well as brain injuries associated with other forms of dementia, in particular macroinfarctions and microinfarctions (i.e. strokes of various sizes).
Here are the highlights of what they found:
The more fish meals per week a subject consumed, the higher their brain mercury level (P < 0.02). There was no correlation between intake of ALA or DHA/EPA supplements and brain mercury level.
For the majority of people (77%) who weren't carriers of the APOE4 allele that increases one's susceptibility to Alzheimer's disease, neither eating fish, dietary DHA/EPA nor consuming ALA had a significant effect (one way or the other) on the risk of Alzheimer's disease.
For the minority (23%) of subjects who were APOE4 carriers, eating more fish and more dietary DHA/EPA was associated with a decreased risk of Alzheimer's disease markers (P < 0.04). Neither DHA/EPA supplements nor dietary ALA impacted Alzheimer's risk in these folks.
Dietary ALA, but not fish or DHA/EPA, was associated with reduced prevalence of macroinfarctions (P < 0.03) and microinfarctions (P < 0.04) associated with non-Alzheimer's cognitive impairment, independent of APOE4 status.
Those were the major, statistically significant findings. There is one more thing I noticed looking at the table below that appears interesting/suggestive for the majority of us who are lucky enough not have the APOE4 gene. The cells I've highlighted below represent the level of various markers of Alzheimer's disease for APOE4-negative folks.
The red cells represent the level of Alzheimer's markers for people who ate the most fish (top red row), or the most dietary DHA/EPA (bottom red row). From the confidence intervals, you can see that none of them are individually significant. But also notice that all of them are positive, meaning there was a trend towards increased markers of Alzheimer's disease in APOE4-negative people who ate the most fish, especially fatty fish.
In contrast, now look at the green cells, representing markers for Alzheimer's disease in APOE4-negative people who consumed the most plant-derived ALA. Notice these too are not individually significant, but all of them are negative, pointing towards a reduced risk of Alzheimer's disease with increasing ALA intake.
From all this, my summary takeaway message from this study would be the following:
For people with the APOE4 gene and therefore increased risk of Alzheimer's disease, eating fish is likely to reduce one's risk of Alzheimer's disease, despite increasing brain mercury levels
For people without the APOE4 gene, fish consumption doesn't seem to reduce, and may even increase, one's risk of Alzheimer's disease
For people without the APOE4 gene, plant-derived omega-3 ALA (e.g. from walnuts, olive oil, flax, chia) consumption may reduce one's risk of Alzheimer's disease
For everyone, dietary ALA appears to reduce one's risk of brain markers for non-Alzheimer's cognitive impairment.
Or more succinctly, ALA is likely to be good for everyone's brain health, and fish is likely to be good for the brain health of only the minority of people who carry the APOE4 allele.
This seems like an illustration of a benefit of getting one's DNA sequenced with a company like 23andMe to determine whether one is a carrier of the APOE4 allele.
--Dean
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[1] JAMA. 2016 Feb 2;315(5):489-97. doi: 10.1001/jama.2015.19451.
Association of Seafood Consumption, Brain Mercury Level, and APOE e4 Status With Brain Neuropathology in Older Adults.
Morris MC, Brockman J, Schneider JA, Wang Y, Bennett DA, Tangney CC, van de Rest O.
Full text: http://jama.jamanetwork.com.sci-hub.io/article.aspx?articleID=2484683
Abstract
IMPORTANCE:
Seafood consumption is promoted for its many health benefits even though its contamination by mercury, a known neurotoxin, is a growing concern.
OBJECTIVE:
To determine whether seafood consumption is correlated with increased brain mercury levels and also whether seafood consumption or brain mercury levels are correlated with brain neuropathologies.
DESIGN, SETTING, AND PARTICIPANTS:
Cross-sectional analyses of deceased participants in the Memory and Aging Project clinical neuropathological cohort study, 2004-2013. Participants resided in Chicago retirement communities and subsidized housing. The study included 286 autopsied brains of 554 deceased participants (51.6%). The mean (SD) age at death was 89.9 (6.1) years, 67% (193) were women, and the mean (SD) educational attainment was 14.6 (2.7) years.
EXPOSURES:
Seafood intake was first measured by a food frequency questionnaire at a mean of 4.5 years before death.
MAIN OUTCOMES AND MEASURES:
Dementia-related pathologies assessed were Alzheimer disease, Lewy bodies, and the number of macroinfarcts and microinfarcts. Dietary consumption of seafood and n-3 fatty acids was annually assessed by a food frequency questionnaire in the years before death. Tissue concentrations of mercury and selenium were measured using instrumental neutron activation analyses.
RESULTS:
Among the 286 autopsied brains of 544 participants, brain mercury levels were positively correlated with the number of seafood meals consumed per week (??=?0.16; P?=?.02). In models adjusted for age, sex, education, and total energy intake, seafood consumption (=?1 meal/week) was significantly correlated with less Alzheimer disease pathology including lower density of neuritic plaques (ß?=?-0.69 score units [95% CI, -1.34 to -0.04]), less severe and widespread neurofibrillary tangles (ß?=?-0.77 score units [95% CI, -1.52 to -0.02]), and lower neuropathologically defined Alzheimer disease (ß?=?-0.53 score units [95% CI, -0.96 to -0.10]) but only among apolipoprotein E (APOE e4) carriers. Higher intake levels of a-linolenic acid (18:3 n-3) were correlated with lower odds of cerebral macroinfarctions (odds ratio for tertiles 3 vs 1, 0.51 [95% CI, 0.27 to 0.94]). Fish oil supplementation had no statistically significant correlation with any neuropathologic marker. Higher brain concentrations of mercury were not significantly correlated with increased levels of brain neuropathology.
CONCLUSIONS AND RELEVANCE:
In cross-sectional analyses, moderate seafood consumption was correlated with lesser Alzheimer disease neuropathology. Although seafood consumption was also correlated with higher brain levels of mercury, these levels were not correlated with brain neuropathology.
PMID: 26836731

All,
As discussed in this thread, evidence suggests ALA may be beneficial for brain health in most people, while DHA/EPA may be a mixed blessing - only helpful for avoid Alzheimer's disease (but not other forms of dementia) in those with the APOE4 allele. And as discussed in this thread, fatty fish high in DHA/EPA may be detrimental for cardiovascular health if contaminated with PCBs, as was the case in several studies of Swedish fish eaters.
But this new study [1] shared by Al Pater (thanks Al!) found in another population of fish eaters, this time from Spain, dietary DHA/EPA may in fact be beneficial for avoiding cardiovascular mortality. But dietary DHA/EPA was not significantly beneficial for all-cause mortality. For dietary Alpha Linolenic Acid (ALA) which is an omega-3 from plants (e.g. walnuts, olive oil, flax, chia seeds) the opposite was the case. Namely, dietary ALA reduced all-cause mortality, but not cardiovascular mortality risk.
Putting the two together, people who met the dietary recommendations for both DHA/EPA and ALA had the lowest all-cause mortality risk - 37% lower than those who didn't meet either recommendation.
Perhaps the fish from Spain have less PCBs than Swedish fish (no - I don't mean the candy :-) ). The full text of the study did not address DHA/EPA supplements - DHA/EPA intake was assessed solely from dietary sources. So it is not clear if a similar beneficial effect could be achieved through a combination of ALA from plant sources and DHA/EPA supplements as fish oil or algae oil, both of which are less likely to be contaminated with mercury or PCBs than the flesh of whole fish.
--Dean
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[1] J Am Heart Assoc. 2016 Jan 26;5(1). pii: e002543. doi: 10.1161/JAHA.115.002543.
Dietary Alpha-Linolenic Acid, Marine Omega-3 Fatty Acids, and Mortality in a Population With High Fish Consumption: Findings From the PREvención con DIeta MEDiterránea (PREDIMED) Study.
Sala-Vila A, Guasch-Ferré M, Hu FB, et al.
http://jaha.ahajournals.org/content/5/1/e002543.long http://jaha.ahajournals.org/content/5/1/e002543.full.pdf+html Abstract BACKGROUND: Epidemiological evidence suggests a cardioprotective role of Alpha-linolenic acid (ALA), a plant-derived Omega-3 fatty acid. It is unclear whether ALA is beneficial in a background of high marine Omega-3 fatty acids (long-chain n-3 polyunsaturated fatty acids) intake. In persons at high cardiovascular risk from Spain, a country in which fish consumption is customarily high, we investigated whether meeting the International Society for the Study of Fatty Acids and Lipids recommendation for dietary ALA (0.7% of total energy) at baseline was related to all-cause and cardiovascular disease mortality. We also examined the effect of meeting the society's recommendation for long-chain n-3 polyunsaturated fatty acids (=/>500 mg/day). METHODS AND RESULTS: We longitudinally evaluated 7202 participants in the PREvención con DIeta MEDiterránea (PREDIMED) trial. Multivariable-adjusted Cox regression models were fitted to estimate hazard ratios. ALA intake correlated to walnut consumption (r=0.94). During a 5.9-y follow-up, 431 deaths occurred (104 cardiovascular disease, 55 coronary heart disease, 32 sudden cardiac death, 25 stroke). The hazard ratios for meeting ALA recommendation (n=1615, 22.4%) were 0.72 (95% CI 0.56-0.92) for all-cause mortality and 0.95 (95% CI 0.58-1.57) for fatal cardiovascular disease. The hazard ratios for meeting the recommendation for long-chain n-3 polyunsaturated fatty acids (n=5452, 75.7%) were 0.84 (95% CI 0.67-1.05) for all-cause mortality, 0.61 (95% CI 0.39-0.96) for fatal cardiovascular disease, 0.54 (95% CI 0.29-0.99) for fatal coronary heart disease, and 0.49 (95% CI 0.22-1.01) for sudden cardiac death. The highest reduction in all-cause mortality occurred in participants meeting both recommendations (hazard ratio 0.63 [95% CI 0.45-0.87]). CONCLUSIONS: In participants without prior cardiovascular disease and high fish consumption, dietary ALA, supplied mainly by walnuts and olive oil, relates inversely to all-cause mortality, whereas protection from cardiac mortality is limited to fish-derived long-chain n-3 polyunsaturated fatty acids. KEYWORDS: fatty acid; nutrition; sudden cardiac death
PMID: 26813890